Golf ball with co-injected cover

ABSTRACT

The present invention is directed towards a multi-layered golf ball cover, formed by a sandwich injection molding process, wherein the multi-layered cover comprises an inner layer, an outer layer, and an intermediate layer sandwiched between the inner and outer layers. The materials of the inner and outer layers may be the same as the intermediate layer, or they may be different with different properties. At least one of layers includes a foaming material.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of co-pending U.S.application Ser. No. 10/641,747 that was filed on Aug. 15, 2003, whichwas a divisional of U.S. application Ser. No. 10/055,232 which was filedJan. 23, 2002 and is now U.S. Pat. No. 6,676,541, and is incorporatedherein in its entirety by express reference thereto.

FIELD OF INVENTION

[0002] The invention relates generally to golf balls, and morespecifically, to a multi-layered golf ball having three cover layersthat are co-injection molded. At least one of the cover layers comprisesa foaming agent.

BACKGROUND OF THE INVENTION

[0003] It is well known that golf balls are typically constructed with acover that tightly surrounds a core. It is typical for a golf ball coreto have a solid construction or a wound construction and the methods offorming these cores are well known in the art. Traditionally, golf ballcovers are formed from polymeric materials. For instance, golf ballshave traditionally incorporated covers made of balata rubber, which maybe a natural balata, a synthetic balata, or a blend of natural andsynthetic balata.

[0004] Other golf balls have incorporated covers which are formed fromsynthetic polymeric materials such as polyolefins and in particular,polyethylene, polyurethanes, and ionic copolymers of olefins. The lattermentioned ionic copolymers of olefins were commercially introduced inthe mid 1960's by E. I. Du Pont de Nemours & Co., Inc., Wilmington, Del.(DuPont) and sold under the trademark “SURLYN.” Golf balls incorporatingSURLYN covers are generally described in U.S. Pat. No. 3,454,280. Covercompositions that are based on SURLYN resins are advantageous in thatthe resulting covers are cut and abrasion resistant compared to thebalata covers. While golf balls incorporating SURLYN resin covers arecommonly known by players to be more cut resistant than balata coveredballs, they traditionally tend to reduce the spin imparted to a golfball and produce a less desirable “feel” as compared to a balata coveredball.

[0005] SURLYN resins sold by DuPont typically contain zinc, lithium,magnesium or sodium ions. A number of SURLYN resins, of varying physicalproperties, are sold by DuPont. The physical properties of these resinsare described in technical bulletins that are readily available fromDuPont. Mixtures of various SURLYN resins as cover stock materials arelikewise highly advantageous. Suitable mixtures for use as covermaterials are described in U.S. Pat. No. 3,819,768.

[0006] For purposes of control, golfers strike a golf ball in such amanner that the ball has substantial backspin. It is desirable that agolfer be able to impart backspin to a golf ball for purposes ofcontrolling its flight and controlling the action of the ball uponlanding on the ground. For example, substantial backspin will make theball stop once it strikes the landing surface instead of boundingforward. The ability to impart back spin onto a golf ball is related tothe deformation of the golf ball cover when struck with a golf club.Generally, the more deformable the cover is, the easier it is to impartspin to the balls. This is particularly true for short or wedge shots.

[0007] Thus, it is desirable to combine the properties of SURLYN coveredgolf balls with the properties of Balata covered golf balls. For exampleit is desirable to have less spin on a drive, such that the ball willhave a “low spin trajectory”. The result is that the ball does not climblike a typical high spin rate ball would, and the ball has substantialroll after it lands on the ground to provide maximum distance. On theother hand, for approach shots, i.e., short shots into the green, spinis critical to control the ball when it lands. With a high spin rate,the ball will stop or “sit” when it hits the green. Thus, with a highspin rate, the ball can be hit directly at the target. With a low spinrate, the ball often bounces off the green or “runs” off the green.Thus, it is desirable to have a high spin rate for approach shots intothe green.

[0008] Further, it is desirable to combine the durability of SURLYNcovered balls with the characteristics of balata covered balls.

[0009] Typically, the golf ball cover layer is formed by one of twoprocesses. The first process includes the compression molding ofhemispheres. First, two hemispherical covers, called half-shells, areinjection molded. The hemispheres are then placed around a core andcompression molded so that they fuse around the core and wherein dimplesare imparted into the cover. The cover is then finished to remove anyvisible molding lines or residue. The second process, called theretractable pin injection molding process, involves injection molding ofthe cover directly around a core positioned on pins, removing the pinsonce the cover material surrounds the core, removing the covered core,and finishing it to form a completed golf ball. In both cover formingprocesses, the injection molding of the covers involves techniques knownin the art. These techniques generally involve forcing molten materialto substantially fill and take on the shape of a mold, thereby forming acover or hemisphere. When the material is cool enough to substantiallymaintain the shape of the mold, it is ejected from the mold.

[0010] Typically, the cover material begins the injection moldingprocess as resin pellets that are stored in a hopper. The pellets aregravity fed into a heated cylinder that melts the pellets as a screwsimultaneously pushes the softening pellets toward an accumulation zone.When enough molten material is accumulated to fill the mold, the screwis pushed or stroked forward, thereby forcing the melted material intothe mold. Many prior art references are directed to mixing differentmaterials to form new cover materials. This is traditionallyaccomplished by mixing pellets of different materials in the injectionmold machine hopper.

[0011] There are also many patents that are directed to golf ballshaving multiple cover layers. For example, U.S. Pat. No. 4,431,193relates to a golf ball having a multilayer cover wherein the inner layeris a hard, high flexural modulus ionomer resin and the outer layer is asoft, low flexural modulus ionomer resin, and wherein either or bothlayers may comprise a foamed ionomer resin.

[0012] U.S. Pat. No. 5,314,187 also relates to golf balls havingmultiple layer covers, wherein the outer layer is molded over the innerlayer and comprises a blend of balata and an elastomer where the innerlayer is an ionomer resin.

[0013] U.S. Pat. No. 4,919,434 is directed towards a golf ball having acover which comprises an inner layer and an outer layer each of which isa thermoplastic resin. Preferably the layers comprise thermoplasticresin materials that are capable of fusion bonding with each other.

[0014] U.S. Pat. No. 5,783,293 discloses a golf ball with amulti-layered cover formed by a co-injection molding process, whereinthe golf ball cover comprises an inner and outer layer of a firstmaterial and an intermediate layer therebetween of a second material.

SUMMARY OF THE INVENTION

[0015] The present invention relates to golf balls having a cover formedby co-injection molding. One embodiment of the present inventionprovides for the cover to consist of three thin layers, an inner layer,an outer layer and an intermediate layer sandwiched between the otherlayers. The cover is formed by a co-injection molded process asdisclosed in U.S. Pat. No. 5,783,293, which is incorporated by referenceherein in its entirety. In a preferred embodiment, the resulting golfball has at least one of the thin layers containing a foamed materialfor a wound core or dual layered, solid core ball.

[0016] Another embodiment of the invention provides for only the outerand inner layers of the outer cover to comprise foamed material. Theouter and inner layers comprised of a different material than theintermediate layer.

[0017] An additional embodiment of the invention provides for theintermediate layer to comprise of the foamed material, with the materialof the inner and outer layers having different physical properties thanthat of the intermediate layer.

[0018] Still another embodiment of the invention provides for all threelayers, outer, inner and intermediate, to be of the same material witheither the inner and outer layers, or the intermediate layer having thefoamed material.

[0019] The cover layer is as thin as 0.005 inches and consist of asandwich configuration. The manipulation of layer thickness and materialselection effects the density, hardness, COR, etc. greatly effects ballperformance.

[0020] The use of thin multi-layers, in combination with gravityadjusting materials creates moment of inertia gradients across the coverlayers.

[0021] The present invention is also directed towards a golf ball havinga multi-layer cover formed by a co-injection molding process, whereby afirst material is divided into an inner layer and an outer layer by aninjected intermediate layer of a second material. More particularly, theinner and outer layers are preferably thinner than the intermediatelayer. The intermediate layer is preferably about ⅖ to ⅘ of the coverthickness and the outer layer is less than about ⅕ of the coverthickness.

[0022] The cover materials each may be a dynamically vulcanizedthermoplastic elastomer, a functionalized styrene-butadiene elastomer, apolyetherester, a polyesterester, a metallocene polymer, a thermoplasticpolyetheramide, a thermoplastic ionomer, a thermoplastic polyester, athermoplastic polyurethane, a ethylene or propylene based polymer, amethyl acrylate, a methyl methacrylate polymer, a polycarbonate, apolyamide, a polyphenylene oxide, a polyether ketone, a polysulfone, anacrylonitrile butadiene polymer, an acrylic styrene-acrylonitrilepolymer, a terphthalate polymer, an ethylenevinyl alcohol polymer, atetrafluoroethylene polymer, a reinforced polymer, or blends thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a golf ball according to an embodiment of the presentinvention disclosing a dual cover, with the inner cover consisting ofthree thin layers of two different materials formed by a co-injectionmolding process.

[0024]FIG. 2 is a golf ball according to FIG. 1, wherein the outer coverconsists of three thin layers formed by a co-injection process.

[0025]FIG. 3 is a ball cover hemisphere.

[0026]FIG. 4 is a golf ball wherein both the inner cover and outercovers consist of three thin layers of two different materials and areformed by a co-injection process.

[0027]FIG. 5 is an elevational sectional view of a multi-materialinjection molding machine for making ball cover hemispheres.

[0028]FIG. 6 is an enlarged section of FIG. 5 showing the plungercompleting the injection of material to form a cover hemisphere.

[0029]FIG. 7 is an enlarged section of FIG. 5 showing the plungercompleting the injection of material to form a cover hemisphere.

[0030]FIG. 8 is an enlarged section of FIG. 5 showing the mold three-wayvalve.

[0031]FIG. 9 is an enlarged section of FIG. 5 showing the mold three-wayvalve.

[0032]FIG. 10 is an elevational sectional view of a multi-materialinjection molding machine for making ball cover hemispheres having a hotrunner system.

DETAILED DESCRIPTION OF THE INVENTION

[0033] Referring to FIGS. 1, 2 and 4, a golf ball 20 having a core 21,an inner cover 22 and an outer cover 23 is shown. FIG. 1 shows the innercover 22 consisting of three thin layers 24, 25 and 26 formed by aco-injection molding machine and process as described in U.S. Pat. No.5,783,293. This process employs a sandwich injection molding machine 40,as shown in FIG. 5, and produces a two-material, golf ball coverhemisphere 30, as depicted in FIG. 3. The layers 24, 25 and 26 are asthin as 0.005 inches and the resulting golf ball 20 will have four coverlayers and a total of five layers for a solid core ball and six totallayers for a wound core or dual core ball. FIG. 2 describes the outercover 23 having three thin layers 27, 28 and 29 formed by theco-injection process. FIG. 4 illustrates the golf ball 20 having bothcovers 22 and 23 each consisting of the three co-injection molded layers24, 25, 26 and 27, 28, 29 respectively. This provides for a ball havingsix cover layers and a total of seven layers for a solid core ball andeight total layers for a wound core or dual core ball. The manipulationof layer thickness and material selection greatly effects the hardness,COR, and moment of inertia which subsequently effects ball performance.The use of gravity adjusting materials, moisture barriers and hardnessgradients will be discussed later.

[0034] Referring to FIG. 5, a sandwich injection-molding machine 40 forproducing a golf ball cover hemisphere 30 having two-materials is shown.The injection molding machine 40 includes two hoppers 41 and 42, anaccumulation chamber 43, a mold 44, a three-way valve 45, and aplurality of channels 46, 47 and 48 interconnecting the same. Moreparticularly, a first hopper 41 contains a first material 31 and asecond hopper 42 contains a second material 32. The three-way valve 45controls the flow direction of the materials 31 and 32. The firstchannel 46 connects the first hopper 41 with the three-way valve 45. Thesecond channel 47 connects the accumulation chamber 43 to the three-wayvalve 45. The third channel 48 connects the three-way valve 45 with themold cavity 50.

[0035] The process comprises the steps of, pellets of a first material31 being loaded into hopper 41, where they feed by gravity or othermeans known in the art to screw 51. Then heat is applied to plasticizethe first material 31 and screw 51 turns within cylinder 52 to pump ameasured amount of plasticized first material 31 through channel 46 tothe three-way valve 45. The material is heated above its melttemperature and preferably to a temperature greater than about 400° F.The three-way valve 45 is positioned such that the flow of the moltenfirst material 31 is fed into the accumulation chamber 43. Theaccumulation chamber 43 is heated such that the material remains in themolten state. Next, the valve 45 selectively permits material flow fromchannel 46 into accumulation chamber 43 (see FIG. 8); and material flowfrom accumulation chamber 43 to mold cavity 50 without diversion backinto channel 46 (see FIG. 9). Pellets of a second material 32 are thenloaded into hopper 42, where they feed by gravity or other means knownin the art to screw 53. Heat is then applied to plasticize the secondmaterial 32. The material is heated above its melt temperature andpreferably to a temperature greater than about 400° F. Screw 53 forces ameasured amount of plasticized second material 32 into accumulationchamber 43, where the second material 32 and the first material 31 arejuxtaposed.

[0036] The first step of the process includes inserting a predeterminedamount of the second material 32 into the heated accumulation chamber 43with the three-way valve 45 closed. Then a predetermined amount of thefirst material 31 is inserted into the accumulation chamber 43 throughthe three-way valve 45 as shown in FIG. 8. Thereafter, the position ofthree-way valve 45 is changed, such that the flow path to channel 46 isclosed, and the flow path through passageway 48 to the mold cavity 50 isopen. A plunger 54 is used to force both the first material 31 and thesecond material 31 past three-way valve 45, through channel 48 and intothe mold cavity 50. The mold cavity 50 is substantially in the shape ofa hemispherical half-shell, and is formed by a mold half 55 and a moldhalf 56.

[0037] Turning to FIG. 6, plunger 54 is translated to the left, pushingmaterials 31 and 32 through valve 45 along channel 48 into mold cavity50. At this point, only the first material 31 has entered the moldcavity 50. The flow is circumferential about the channel 48. The moldhalves 55 and 56 are cooled so that the molten material solidifies inthe mold cavity 50. Preferably, the mold halves 55 and 56 are maintainedat a temperature below about 100° F. Most preferably, the mold halvesare maintained at a temperature below 50° F. so that the molten materialfreezes to the mold walls 57 and 58. First material 31, thus, flows intothe mold cavity 50 and substantially adheres to the cavity surfaces 57and 58 of mold cavity 50. Since there is a sharp temperature gradient inthe first material 31, hot in the center and cold on the edges againstthe mold halves 55 and 56, the flow of material is much easier throughthe center. The material must be pushed into the mold cavity 50 withsufficient pressure to allow the material to fill the cavity 50 beforeit solidifies.

[0038] Referring now to FIG. 7, second material 32 with the firstmaterial 31 substantially fills the mold cavity 50. The second material23 follows the first material 31. The mold 44 is maintained at atemperature much lower than the melting temperature of the firstmaterial 31, generally a temperature of less than 100° F., andpreferably about 50° F. Because of this the first material 31 solidifiesagainst the surfaces 57 and 58 of the mold cavity 50 as it flows intothe mold cavity 50. Flow into the mold cavity 50 is, thus, through themiddle or center of the first material 31. Since the second material 32follows the first material 31, it flows through the center of the innerand outer layers 24 and 26, forming an intermediate layer 25 (see FIG.3). In order to increase the thickness of the inner and outer layers 24and 26, more first material 31 can be used and the flow rate into themold decreased. To make thinner inner and outer layers 24 and 26, lessfirst material 31 is used and the flow rate into the mold increased.Preferably, the intermediate layer 25 comprises about ⅖ to ⅘ of thecover thickness with the outer layer 26 comprising about ⅕ or less ofthe thickness.

[0039] Once the materials 31 and 32 cool enough to substantially retainthe shape of the mold cavity, the mold halves 55 and 56 are separated,and an ejector 61 (see FIG. 5) ejects a two material, three-layerhemisphere 30 (see in FIG. 3) from the injection molding machine 40.

[0040] Referring to FIG. 1, a completed golf ball 20 according to thepresent invention is shown. Core 21 is surrounded by the inner cover 22which is comprised of two three-layer hemispheres 30 which have beencompression molded together, thereby forming compression molding seam60. Compression molding hemispheres onto a core generally involvesapplying pressure and heat to mold the cover hemispheres onto the coreand is known in the art. It is contemplated that the core 21 is a solid,polybutadiene type core, a solid core having multiple layers or a woundcore.

[0041] It is contemplated that first material 31 and second material 32each comprise one or more polymers. Useful polymers include athermoplastic ionomer, a dynamically vulcanized thermoplastic elastomer,a functionalized styrene-butadiene elastomer, a polyetherester, apolyesterester, a metallocene polymer, a thermoplastic polyetheramide, athermoplastic polyester, a thermoplastic polyurethane, an ethylene orpropylene based polymer, a methyl acrylate, a methyl methacrylatepolymer, a polycarbonate, a polyamide, a polyphenylene oxide, apolyether ketone, a polysulfone, an acrylonitrile butadiene polymer, anacrylic styrene-acrylonitrile polymer, a terphthalate polymer, anethylenevinyl alcohol polymer, a tetrafluoroethylene polymer, areinforced polymer, or blends thereof. As noted above, the first andsecond layers should be different polymers or be polymers that havedifferent properties.

[0042] Most preferably the first material 31 and second material 32 arecomprised of thermoplastic ionomers or of a balata rubber and athermoplastic ionomer, respectively. Suitable thermoplastic ionomerresins include any number of olefinic based ionomers including SURLYN®and IOTEK®, which are commercially available from DuPont and Exxon,respectively.

[0043] Among the preferred materials for first material 31 and/or secondmaterial 32 are ionomer resins obtained by providing a cross metallicbond to polymers of monoolefin with at least one member selected fromthe group consisting of unsaturated mono- or di-carboxylic acids having3 to 12 carbon atoms and esters thereof (the polymer contains 1 to 50%by weight of the unsaturated mono- or di-carboxylic acid and/or esterthereof). More particularly, such acid-containing ethylene copolymerionomer component of the subject invention includes E/X/Y copolymerswhere E is ethylene, X is a softening comonomer such as an acrylate,e.g., methyl acrylate, iso-butyl acrylate or n-butyl acrylate, presentin 1-60 (preferably 10-40, most preferably 10-25), weight percent of thepolymer, and Y is ethylenically unsaturated organic acid, such asacrylic or methacrylic acid, present in 5-35 (preferably 10-35, mostpreferably 10-21) weight percent of the polymer, wherein the acid moietyis neutralized 1-90% (preferably at least 40%, most preferably at leastabout 60%) to form an ionomer by a cation such as lithium, sodium,potassium, magnesium, calcium, barium, lead, tin, zinc or aluminum, or acombination of such cations. Lithium, sodium, magnesium and/or zinc arepreferred.

[0044] Specific acid-containing ethylene copolymers includeethylene/acrylic acid, ethylene/methacrylic acid, ethylene/acrylicacid/n-butyl acrylate, ethylene/methacrylic acid/n-butyl acrylate,ethylene/methacrylic acid/iso-butyl acrylate, ethylene/acrylicacid/iso-butyl acrylate, ethylene/methacrylic acid/n-butyl methacrylate,ethylene/acrylic acid/methyl methacrylate, ethylene/acrylic acid/methylacrylate, ethylene/methacrylic acid/methyl acrylate,ethylene/methacrylic acid/methyl methacrylate, and ethylene/acrylicacid/n-butyl methacrylate. Preferred acid-containing ethylene copolymersinclude ethylene/methacrylic acid, ethylene/acrylic acid,ethylene/methacrylic acid/n-butyl acrylate, ethylene/acrylicacid/n-butyl acrylate, ethylene/methacrylic acid/methyl acrylate andethylene/acrylic acid/methyl acrylate copolymers. The most preferredacid-containing ethylene copolymers are ethylene/methacrylic acid,ethylene/acrylic acid, ethylene/(meth)acrylic acid/n-butyl acrylate,ethylene/(meth)acrylic acid/ethyl acrylate, and ethylene/(meth)acrylicacid/methyl acrylate copolymers.

[0045] The manner in which the ionomers are made is well known in theart as described, e.g., in U.S. Pat. No. 3,262,272. Such ionomer resinsare commercially available from DuPont Co. under the trade name SURLYN®.

[0046] Additionally, foamed polymeric materials, in particular,metallocene-based foam resins are suitable for use in the cover layersof the present invention.

[0047] Still further, the first or second materials 31 or 32 can becomprised of balata rubber or of a synthetic balata.

[0048] In the present invention, first material 31 has a melting pointor heat of reaction (cure) temperature that is similar to that of secondmaterial 32. Alternatively, first material 31 has a melting point orheat of reaction temperature that is higher than that of second material32, but at a temperature which does not cause degradation of secondmaterial 32. In another alternative embodiment, second material 32 has amelting point or heat of reaction temperature that is higher than thatof first material 31, but at a temperature which does not causedegradation of first material 31.

[0049] Various examples of golf balls according to the present inventionare set forth below.

EXAMPLE 1

[0050] A polybutadiene core 21 having a diameter of about 1.50 to 1.55inches can be covered with a three-layer cover comprised of thefollowing: FIRST SECOND MATERIAL 11 MATERIAL 21 Material SURLYN 7930SURLYN 8320 Composition 30% 70% Tensile Strength, psi 3,800 3,100Tensile Strain @ 290 770 Break, % Flexural Modulus, psi 67,000 2,800Melt Flow, g/10 min 1.8 0.9 Hardness, Shore D 68 25 Bashore Resilienc 5342

[0051] This example can be formed by forming cover hemispheres in amold. The first and second materials should be heated to approximately400-425° F. and injected into a 40° F. mold. The first material willadhere to the surfaces of the mold to form the inner and outer layers ofthe cover hemisphere and the second material will flow between the innerand outer layers to form an intermediate layer. The two hemispheres canbe compression molded about the polybutadiene core to form the innercover of the ball. The inner cover is preferably formed to an outerdiameter of about 1.55 to 1.64 inches.

[0052] Then an outer cover comprised of a thermoset urethane such asthat described in U.S. Pat. Nos. 5,334,673 and 6,210,294 or a polyureamaterial such as that described in U.S. Pat. No. 5,484,870 can be castover the inner cover layer. These patents are incorporated by referenceherein in their entirety.

[0053] Preferably, the outer cover has a hardness of about 50 to 65shore D when measured on the ball. The outer cover material of thisexample preferably has a flexual modulus of about 5,000 to 30,000 psi.

[0054] In an alternate embodiment the first and second materials can beinversed.

EXAMPLE 2

[0055] A polybutadiene core having a diameter of about 1.50 to 1.55inches is covered with an inner cover, which is covered by a three-layerouter cover comprised of the following: FIRST SECOND MATERIAL 11MATERIAL 21 Material SURLYN 8320 SURLYN 7930 Composition 30% 70% TensileStrength, psi 3,100 3,800 Tensile Strain @ 770 290 Break, % FlexuralModulus; psi 2,800 67,000 Melt Flow, g/10 0.9 1.8 Hardness, Shore D 2568 Bashore Resilience 42 53

[0056] A golf ball core can be covered with an inner cover such as thosedescribed in U.S. Pat. No. 5,688,191, which is incorporated herein inits entirety. Preferably, an inner cover comprising a dynamicallyvullcanized thermoplastic elastomer, functionalized styrene-butadieneelastomer, metallocene polymer or blends thereof is formed over the coresuch that the inner cover has an outer diameter of about 1.55 to 1.62inches.

[0057] This example was formed by first forming cover hemispheres in amold. The first and second materials were heated to approximately 400°F.-425° F. and injected into a 40° F. The first material adhered to thesurfaces of the mold to form the inner and outer layers of the coverhemisphere and the second material flowed between the inner and outerlayers to form an intermediate layer. The two hemispheres were thencompression molded about the inner cover to form the outer cover.

EXAMPLE 3

[0058] A polybutadiene core having a diameter of 1.560 inches can becovered with a thin three layer inner cover of the material compositionlisted in Example 1 above, and a three layer outer cover of the materialcomposition listed in Example 2 above.

[0059] This example was formed by first forming the inner coverhemispheres as described in Example 1 and compression molding them aboutthe polybutadiene core, and then forming the outer cover hemispheres asdescribed in Example 2 and molding them about the inner cover to form agolf ball having a total of 7 layers.

EXAMPLE 4

[0060] A polybutadiene core having a diameter of 1.560 inches is coveredwith a thin three layer inner cover of the material composition aslisted in Example 2 above, and a three layer outer cover of the materialcomposition listed in Example 1 above.

[0061] This example can be made by first, forming the inner coverhemispheres, as described in Example 2, and compression molding themabout the polybutadiene core. Then forming the outer cover hemispheresas described in Example 1 and molding them about the inner cover to forma golf ball having a total of 7 layers.

[0062] The materials Surlyn 7930 and 8320 are registered trademarks ofthe DuPont Company. The golf balls in the examples were constructedusing a compression molding method. However, it will be apparent tothose skilled in the art that the golf balls can also be constructed bythe retractable pin injection molding process, which involves injectionmolding of the cover directly around a core positioned on pins. The pinsare removed once the cover material surrounds the core and hassolidified to the extent the core will not move. In this process, thecompression molding seam 60 can be eliminated. After the cover materialshave hardened, the covered core is removed and finished to form acompleted golf ball. Based on the teachings herein, the necessarymodifications to the standard retractable pin injection moldingprocesses will be readily apparent to those skilled in the art.

[0063] Optionally, one or more of the inner layers may serve as moisturebarrier layers that will protect against reduced COR values, due tomoisture take-up by the core 21. Preferably one of the intermediatelayers 25, 28 may serve as a moisture barrier layer, more preferably theintermediate layer 25 will serve as the moisture barrier. The use ofmoisture barriers is described in co-pending patent application Ser. No.09/973,342, which is incorporated by reference herein in its entirety.

[0064] A moisture barrier should have a moisture vapor transmission ratethat is less than that of the outer cover layer, and more preferably,less than the moisture vapor transmission rate of an ionomer resin suchas Surlyn®, which has a rate in the range of about 0.45 to about 0.95grams per mm/m² per day. The moisture vapor transmission rate is definedas: the mass of moisture vapor that diffuses into a material of a giventhickness per unit area per unit time. The preferred standards ofmeasuring the moisture vapor transmission rate include: ASTM F1249-90entitled “Standard Test Method for Water Vapor Transmission Rate ThroughPlastic Film and Sheeting Using a Modulated Infrared Sensor,” and ASTMF372-99 entitled “Standard Test Method for Water Vapor Transmission Rateof Flexible Barrier Materials Using an Infrared Detection Technique,”among others.

[0065] The manipulation of moment of inertia via the filling (or foamingor otherwise reducing specific gravity) of the core 21 and cover layers24-29 provide the opportunity to further improve upon distance and spin.The low specific gravity core 21 or layers 24-29 can be made from anumber of suitable materials, so long as the low specific gravitycontributes to the soft compression and resilience of the golf ball. Thematerial can be from a thermosetting syntactic foam with hollow spherefillers or microspheres in a polymeric matrix of epoxy, urethane,polyester or any suitable thermosetting binder, where the curedcomposition has a specific gravity less than 1.1 g/cc and preferablyless than 1.0 g/cc. Additionally, any number of foamed or otherwisespecific gravity reduced thermoplastic or thermosetting polymercompositions or foaming agents may also be used such asmetallocene-catalyzed polymers and blends thereof described in U.S. Pat.Nos. 5,824,746 and 6,025,442 which are incorporated by reference hereinin their entirety. Further, a thermoset polyurethane composition havinga specific gravity or less than 1.3 g/cc such as a nucleated reactioninjection molded or cast polyurethane may be used. Such a compositionmay result in a gas-filled or cellular solid layer.

[0066] As discussed in U.S. Pat. No. 5,971,870, which is incorporated byreference herein in its entirety, fillers may be or are typically in afinely divided form. For example, in a size generally less than about 20mesh, preferably less than about 100 mesh U.S. standard size, except forfibers and flock, which are generally elongated, flock and fiber sizesshould be small enough to facilitate processing. Filler particle sizewill depend upon desired effect, cost, ease of addition, and dustingconsiderations. The filler preferably is selected from the groupconsisting of precipitated hydrated silica, clay, talc, asbestos, glassfibers, aramid fibers, mica, calcium metasilicate, barium sulfate, zincsulfide, lithopone, silicates, silicon carbide, diatomaceous earth,polyvinyl chloride, carbonates, metals, metal alloys, tungsten carbide,metal oxides, metal stearates, particulate carbonaceous materials, microballoons, and combinations thereof. Non-limiting examples of suitablefillers, their densities, and their preferred uses are as follows: Sp.Gr. Comments Filler Type Precipitated hydrated silica 2.0 1, 2 Clay 2.621, 2 Talc 2.85 1, 2 Asbestos 2.5 1, 2 Glass fibers 2.55 1, 2 Aramidfibers (KEVLAR ®) 1.44 1, 2 Mica 2.8 1, 2 Calcium metasilicate 2.9 1, 2Barium sulfate 4.6 1, 2 Zinc sulfide 4.1 1, 2 Lithopone 4.2-4.3 1, 2Silicates 2.1 1, 2 Silicon carbide patelets 3.18 1, 2 Silicon carbidewhiskers 3.2 1, 2 Tungsten carbide 15.6 1 Tungsten oxide 5.8 1Diatomaceous earth 2.3 1, 2 Polyvinyl chloride 1.41 1, 2 CarbonatesCalcium carbonate 2.71 1, 2 Magnesium carbonate 2.20 1, 2 Metals andAlloys (powders) Titanium 4.51 1 Tungsten 19.35 1 Aluminum 2.70 1Bismuth 9.78 1 Nickel 8.90 1 Molybdenum 10.2 1 Iron 7.86 1 Steel 7.8-7.91 Lead 11.4 1, 2 Copper 8.94 1 Brass 8.2-8.4 1 Boron 2.34 1 Boroncarbide whiskers 2.52 1, 2 Bronze 8.70-8.74 1 Cobalt 8.92 1 Beryllium1.84 1 Zinc 7.14 1 Tin 7.31 1 Metal Oxides Zinc oxide 5.57 1, 2 Ironoxide 5.1 1, 2 Aluminum oxide 4.0 Titanium oxide 3.9-4.1 1, 2 Magnesiumoxide 3.3-3.5 1, 2 Zirconium oxide 5.73 1, 2 Metal Stearates Zincstearate 1.09 3, 4 Calcium stearate 1.03 3, 4 Barium stearate 1.23 3, 4Lithium stearate 1.01 3, 4 Magnesium stearate 1.03 3, 4 Particulatecarbonaceous materials Graphite 1.5-1.8 1, 2 Carbon black 1.8 1, 2Natural bitumen 1.2-1.4 1, 2 Cotton flock 1.3-1.4 1, 2 Cellulose flock1.15-1.5  1, 2 Leather fiber 1.2-1.4 1, 2 Micro balloons Glass 0.15-1.1 1, 2 Ceramic 0.2-0.7 1, 2 Fly ash 0.6-0.8 1, 2 Coupling Agents AdhesionPromoters Titanates 0.95-1.11 Zirconates 0.92-1.11 Silane 0.95-1.2 

[0067] Referring to FIG. 10, golf ball cover hemispheres can also bemolded in sandwich injection-molding machine 70 that includes twoaccumulation chambers 72 and 74 for materials 31 and 32. This sandwichinjection-molding machine also includes two mold halves 76 and 78 toform a plurality of mold cavities 80. However, this machine furtherincludes a hot runner system 82 comprised of a hot manifold 84 and hotrunners 86 and 88 interconnecting the accumulation chambers 72 and 74with the mold cavities 80. The hot runners 86 and 88 are maintained at atemperature above the melting point of the materials 31 and 32 so thatthe material does not solidify therein. A predetermined amount of thefirst material 31 is fed into the accumulation chamber 72 and injectedthrough the hot runner system 86 into the mold cavities 80. Then apredetermined amount of the second, different material 32 is injectedfrom accumulation chamber 74 through hot runner system 88 and into themold cavities 80. This eliminates the waist that is created in the coldrunner 35 discussed above and creates a quicker molding method.

[0068] Foaming agents may manipulate the moment of inertia and provideimprovement upon distance and spin. As stated above the co-injectionmolding may produce a cover of three thin layers utilizing two differentmaterials. The use of dissimilar materials together generates uniqueproperties. A soft outer layer over a hard middle layer can yield a ballhaving improved spin when the ball is struck by a club such as a wedge,yet it still can maintain medium spin and excellent velocity when struckby a driver. When used in this way foaming agents reduce the hardnessand modulus of the resultant cover.

[0069] In a co-injected molded cover of this invention, as best seen onFIG. 2, foaming agents when used in the middle layer improve feel andchange the moment of inertia, and when they are used in the inner andouter layers they increase spin and control moment of inertia.

[0070] Co-injection molding having a foamed layer allows for a multitudeof variations regarding spin, moment of inertia and velocity. Examplesof possible combinations include: very thin inner and outer layers(0.005″ to 0.015″) over a thick or thin foamed middle layer; thick innerand outer layers over a thin inner layer; and each layer having the samethickness. These different thicknesses of polymers can be made by amultitude of materials, such as hard SURLYN® over and under soft, foamednon-ionomeric materials; or foamed SURLYNS® over and under hardresilient ionomer. The foamed cover layer can be used over a solid,one-piece core; a solid, dual core; or a wound ball (with a solid orliquid center). The co-injection molded cover could also combinedifferent groups of thermoplastic materials such as: ionomers, blockcopolymers, non-ionomers, thermoplastic urethanes, and metallocenes, andblends of those materials. These materials may also be loaded withgravity adjusting materials to improve moment of inertia.

[0071] Golf balls were made and test conducted to determine how a golfball cover would be affected by the introduction of a foaming agent intothe composition of the cover material. The covers were made usingvarying blends of SURLYN® and FUSABOND® which are available from DuPont,and the foaming agent ACTIVEX 535, available from Boehringer IngelheimChemicals, Petersburg, Va.

[0072] Six different blends of material for golf ball covers were madeand tested. The results appear in the following Tables. “40 HOUR” DATAFlex Tensile Modulus Modulus Stress Strain @ Strain @ Strain @ BlendDensity (ksi) (ksi) @ Yield Yield Break Break No. (g/cm³) [act hrs] [acthrs] (ksi) (%) (ksi) (%) 1 0.942 54.3(1.2) 41.35 2.13 17.68 2.86 152.7[49.25] (4.25) (0.11) (1.67) (1.310) (20.3) 2 0.942 53.8(1.4) 38.57 2.1915.33 2.64 138.9 [48] (4.09) (0.10) (0.67) (0.06) (13.5) 3 0.94851.6(0.9) 38.57 2.19 17.14 3.22 192.0 [47.75] (4.09) (0.10) (1.94)(0.15) (11.7) 4 0.933 37.4(1.3) 26.22 1.91 17.24 2.69 201.3 [46.5](2.24) (0.01) (1.65) (0.02) (15.6) 5 0.936 35.7(1.3) 24.28 1.83 17.702.73 187.5 [37.5] (1.07) (0.03) (1.33) (0.22) (10.9) 6 0.940 35.9(1.0)27.77 1.93 16.37 2.84 188.8 [39] (2.74) (0.01) (1.19) (0.68) (6.9)

[0073] 2 WEEK DATA % Flex Tensile Stress Strain @ Stress Strain @ BlendActivex Modulus Modulus @ Yield Yield @ Break Break No. 535 (ksi) (ksi)(ksi) (ksi) (ksi) (%) 1 0 60.74 56.46 2.47 11.33 2.30 155.8 (0.39)(11.94) (0.02) (0.55) (0.15) (15.3) 2 1 58.66 42.87 2.43 12.88 2.48163.1 (1.01) (4.53) (0.02) (0.40) (0.06) (7.7) 3 3 56.61 38.51 2.3613.18 2.97 205.2 (0.71) (5.23) (0.02) (0.68) (0.05) (13.1) 4 0 40.9929.37 1.82 18.59 2.39 211.2 (0.34) (4.69) (0.02) (2.09) (0.03) (11.3) 51 40.47 26.79 1.80 19.13 2.24 219.6 (0.30) (2.84) (0.01) (3.64) (0.53)(28.4) 6 3 40.05 25.41 1.80 19.27 2.32 216.5 (0.30) (2.65) (0.02) (2.76)(0.15) (12.4)

[0074] The blends were comprised of the following materials:

[0075] (1) 50% SURLYN 7940® and 50% SURLYN 8940®;

[0076] (2) 49.5% 7940®, 49.5% 8940®, and 1% Activex 535®;

[0077] (3) 48.5% 7940®, 48.5% 8940®, and 3% Activex 535®.

[0078] (4) 35% 7940®, 45% 8945®, 20%, and Fusabend 525D®;

[0079] (5) 35% 7940®, 44% 8945®, 20% 525D® and 1% Activex 535®; and

[0080] (6) 35% 7940®, 42% 8945®, 20% 525D® and 3% Activex 535®.

[0081] It is fairly apparent that the introduction of a foaming agentinto the composition of the cover material significantly lowers the flexand tensile moduli and also the stress yield of the ball.

[0082] While it is apparent that the illustrative embodiments of theinvention herein disclosed fulfills the objectives stated above, it willbe appreciated that numerous modifications and other embodiments may bedevised by those skilled in the art. Therefore, it will be understoodthat the appended claims are intended to cover all such modificationsand embodiments which come within the spirit and scope of the presentinvention.

We claim:
 1. A golf ball comprising: a core of one or more layers; aco-injected molded cover comprising inner, outer and intermediatelayers; the inner and outer layers of the cover comprising of a firstmaterial having at least one polymer; and the intermediate layer of thecover comprising of a second material having at least one polymerincluding a foamed polymer therein, wherein the second material hasdifferent physical properties than the first material.
 2. The golf ballof claim 1, wherein the inner and outer layers of the cover have athickness that is less than that of the intermediate layer.
 3. The golfball of claim 2, wherein the inner and outer layers of the cover have athickness that is less than 0.015 inch.
 4. The golf ball of claim 1,wherein the inner and outer layers of the cover have a thickness that isgreater than that of the intermediate layer.
 5. The golf ball of claim1, wherein the inner, outer and intermediate layers of the cover are ofgenerally equal thickness.
 6. The golf ball of claim 1, wherein thefirst material is comprised of one or more polymers selected from thegroup consisting of a thermoplastic ionomer, a dynamically vulcanizedthermoplastic elastomer, a functionalized styrene-butadiene elastomer, apolyetherester, a polyesterester, a metallocene polymer, a thermoplasticpolyetheramide, a thermoplastic polyester, a thermoplastic polyurethane,a ethylene or propylene based polymer, a methyl acrylate, a methylmethacrylate polymer, a polycarbonate, a polyamide, a polyphenyleneoxide, a polyether ketone, a polysulfone, a acrylonitrile butadienepolymer, a acrylic styrene-acrylonitrile polymer, a terphthalatepolymer, a ethylene-vinyl alcohol polymer, a tetrafluoroethylenepolymer, a reinforced polymer, and blends thereof.
 7. The golf ball ofclaim 1, wherein the second material is comprised of one or morepolymers selected from the group consisting of a thermoplastic ionomer,a dynamically vulcanized thermoplastic elastomer, a functionalizedstyrene-butadiene elastomer, a polyetherester, a polyesterester, ametallocene polymer, a thermoplastic polyetheramide, a thermoplasticpolyester, a thermoplastic polyurethane, a ethylene or propylene basedpolymer, a methyl acrylate, a methyl methacrylate polymer, apolycarbonate, a polyamide, a polyphenylene oxide, a polyether ketone, apolysulfone, a acrylonitrile butadiene polymer, a acrylicstyrene-acrylonitrile polymer, a terphthalate polymer, a ethylene-vinylalcohol polymer, a tetrafluoroethylene polymer, a reinforced polymer,and blends thereof.
 8. The golf ball of claim 1, wherein the core issolid and comprised of more than one layer.
 9. The golf ball of claim 1,wherein the core is a wound core.
 10. The golf ball of claim 1, whereinthe core is a dual core.
 11. A golf ball comprising: a core of one ormore layers; a co-injected molded cover comprising inner, outer, andintermediate layers; the inner and outer layers comprising of a firstmaterial at least one polymer and including a foamed polymer; and theintermediate layer comprising of a second material having at least onepolymer, wherein the second material has different physical propertiesthan the first material
 12. The golf ball according to claim 11, whereinthe inner and outer layers of the cover have a thickness that is lessthan that of the intermediate layer.
 13. The golf ball of claim 11,wherein the first material is comprised of one or more polymers selectedfrom the group consisting of a thermoplastic ionomer, a dynamicallyvulcanized thermoplastic elastomer, a functionalized styrene-butadieneelastomer, a polyetherester, a polyesterester, ametallocene+thermoplastic polyurethane, an ethylene or propylene basedpolymer, a methyl acrylate, a methyl methacrylate polymer, apolycarbonate, a polyamide, a polyphenylene oxide, a polyether ketone, apolysulfone, an acrylonitrile butadiene polymer, an acrylicstyrene-acrylonitrile polymer, a terphthalate polymer, an ethylene-vinylalcohol polymer, a tetrafluoroethylene polymer, a reinforced polymer,and blends thereof.
 14. The golf ball of claim 11, wherein said secondmaterial is comprised of one or more polymers selected from the groupconsisting of a thermoplastic ionomer, a dynamically vulcanizedthermoplastic elastomer, a functionalized styrene-butadiene elastomer, apolyetherester, a polyesterester, a metallocene polymer, a thermoplasticpolyetheramide, a thermoplastic polyester, a thermoplastic polyurethane,an ethylene or propylene based polymer, a methyl acrylate, a methylmethacrylate polymer, a polycarbonate, a polyamide, a polyphenyleneoxide, a polyether ketone, a polysulfone, an acrylonitrile butadienepolymer, an acrylic styrene-acrylonitrile polymer, a terphthalatepolymer, an ethylene-vinyl alcohol polymer, a tetrafluoroethylenepolymer, a reinforced polymer, and blends thereof.
 15. The golf ballaccording to claim 11, wherein the core is a solid core.
 16. The golfball according to claim 11, wherein the core is a wound core.
 17. Thegolf ball according to claim 11, wherein the core is solid and comprisedof more than one layer.
 18. A golf ball comprising: a core of one ormore layers; a co-injected molded cover having inner, outer andintermediate layers, each layer formed of a material comprising at leastone polymer; and the material of the intermediate layer containing afoamed polymer.
 19. A golf ball comprising: a core of one or morelayers; a co-injected molded cover comprising inner, outer andintermediate layers, each layer formed of a material having at least onepolymer; and the material of the inner and outer layers containing afoamed polymer.